The invention relates to a control device and a method for establishing the rotor angle of a synchronous machine, in particular at standstill of a synchronous machine of an electric drive system of an electrically operated vehicle.
It is becoming apparent that, in the future, electronic systems that combine new energy storage technologies with electric drive technology will be used increasingly both in stationary applications, such as in wind turbines or solar installations, and in vehicles, such as hybrid or electric vehicles.
When regulating a synchronous machine, for example in an electric drive system of an electrically operated vehicle, the knowledge of the position of the rotor relative to the stator of the synchronous machine plays a central role. In order to provide a required torque with a synchronous machine, a rotating electric field is generated in the stator of the machine and rotates synchronously with the rotor. For the generation of this field, the current angle of the rotor is required for the regulation process.
One possibility for determining the rotor angle lies in the implementation of a sensor in the synchronous machine, said sensor being able to detect the rotor angle. Exemplary sensor types include incremental sensors, resolvers, Vogt sensors and digital Hall sensors.
A further possibility for determining the rotor angle lies in sensorless determination methods. For example, different methods for sensorless determination of a rotor angle of a synchronous machine are known from the documents by Schroedl, M.: “Sensorless control of AC machines at low speed and standstill based on the INFORM method”, Industry Applications Conference, 1996, 31st IAS Annual Meeting; Ostlund, M., Brokemper, M.: “Initial rotor position detections for an integrated PM synchronous motor drive”, Industry Applications Conference, 1995, 30th IAS Annual Meeting; Linke, M., Kennel, R., Holtz, J.: “Sensorless speed and position control of synchronous machines using alternating carrier injection”, Electric Machines and Drives Conference, 2003, IEMDC'03; and Braun, M., Lehmann, O., Roth-Stielow, J.: “Sensorless rotor position estimation at standstill of high speed PMSM drive with LC inverter output filter”, 2010 IEEE International Conference on Industrial Technology (ICIT).
Documents DE 10 2008 042 360 A1 and WO/2009/047217 A2 each disclose a method for determining the rotor angle of a synchronous machine at standstill with the aid of iterative test pulses.